The present invention relates to a device for sensing the level of a liquid within a container. More particularly, the present invention relates to a device able to detect the presence of lubricating oil of an engine within the interior of an associated reservoir such as, for example, the oil collection sump thereof.
Numerous level sensing devices are known in commerce, which provide an indication of electrical type when the level of the liquid under test falls below a minimum predetermined value. There are, for example, known sensors which utilize a pair of bimetal elements mounted at the end of a rod which is held immersed in the container; on one of these elements there is wound a resistor which is periodically supplied with electric current in such a way as to generate a localized heating of one of the two bimetal elements. Depending on whether or not these elements are immersed in the liquid, there will occur a dispersion of the heat developed in the mass of liquid or else a concentration of the heat on the bimetallic element. In the first case the bimetal element does not show any practical effects of the variation of heat and therefore does not deform, whereas in the second case the localized variation of temperature causes a deformation of the bimetal element and consequent opening of the electrical contact, is established by this latter. The disadvantages presented by devices of the above specified type are principally connected with the criticality of intervention and the cost of the devices themselves, which require for their operation a suitable electronic circuit to supply them.
There are likewise known sensor devices which essentially comprise a magnet supported by a tubular float, and a magnetically actuable electric contact element supported by a suitable element, which also performs the function of constituting the guide for displacements of the float under the action exerted by the hydrostatic thrust of the liquid. It is observed, however, that such devices are hardly used in the detection of the level of oil because the viscosity of this liquid creates a high surface tension between the float and the associated support element, making excursions of the first with respect to the second difficult and therefore involving a low precision or indication of the predetermined level.